1. Field of Invention
The present invention relates to an apparatus for heating a medical fluid, a method for heating a medical fluid, and a blood treatment device.
2. Description of the Prior Art
In the extracorporeal blood treatment it is necessary to temper the processed fluids, in order to prevent cooling down of the patient. In the extracorporeal dialysis treatments of the blood the dialysis fluid, or further fluids, such as e.g. substitution fluids, generally are brought to a corresponding temperature, in order to prevent the blood in the extracorporeal circuit from cooling down too much.
The tempering of dialysis fluids also can be found in treatment systems of the peritoneal dialysis. The dialysis fluid is administered into the peritoneum of the patient and must be tempered correspondingly. Various treatment modes are known, in which the dialysis fluid must be supplied to the patient according to automated flow schemes and the dialysis fluid must be tempered corresponding to the flow scheme.
Both in the hemodialysis and in the peritoneal dialysis, systems are under development and already state of the art, in which hydraulic and thermal functional elements for processing the dialysis fluid or other physiological fluids, such as e.g. substitution fluid (EN), are provided on disposable articles. The use of disposable articles, which generally are made of plastics, imposes particular requirements on the control of the heat source.
It should be noted that the temperature control of fluids in disposable articles is a slow process. The poor heat transfer in the disposable article in addition requires high temperatures at the heater interface. So, it is not uncommon that a fluid temperature of 40° C. requires a temperature of the heating plate of more than 80° C.
When the flow is interrupted due to the process or an alarm, the fluid is present at the hot interface and can be overheated. This can lead to the fact that the heater is or must be switched off in the case of a flow standstill. During short standstill times overheating and hence a condition requiring an alarm nevertheless can occur. During long standstill times, the fluid will cool down more.
EP 0 956 876 A1 discloses a disposable cassette for the peritoneal dialysis for delivering and tempering the dialysis fluid.
US 2009/012655 A1 discloses a controlled heating element for tempering dialysis fluid on a dialysis cassette. The heating element is actuated on the basis of a temperature deviation and the flow rate of the dialysis fluid.
EP 0 254 801 B1 discloses a fluid heater with means for determining the fluid temperature, the heater temperature and the temperature of an interconnected heating plate. Switching off is effected when heater or heating plate are too hot, in particular when there is a strongly reduced flow of the fluid.